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K. Chalam, S. Balaiya Mehanathan, R. Keshavamurthy; Evaluation of Differential Sensitivity of Retinal and Choroidal Cells to Proton Beam Radiation: A Model for Age Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4945.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the effects of varying doses of proton beam radiation on the survival of choroidal endothelial cells and Retinal ganglion cells.
Retinal ganglion cell (RGC-5) and choroidal endothelial cells (RF6A) were exposed to different durations as well as intensities of proton beam radiation. Increasing dose of radiation (2Gy, 4Gy, 8Gy and 12Gy) was delivered in a single fraction. Viability of each cell line, post radiation was determined using trypan blue exclusion assay with Vi-cell count at days 5, 9 and 12. Cell proliferation was assessed using neutral red (NR) uptake assay. Radiation induced DNA damage was assessed indirectly by measuring the production of reactive oxygen species (ROS), with dihydrorhodamine 123.
RF6A cells exposed to 8 Gy radiation showed 80% viability at day 5 which decreased to 21% at day 9. Only 4% cells were viable at 12Gy compared with control at day 9. In the RGC-5 cell line, 57% cell viability was noted at day 5 after exposure to 8Gy which decreased to 36% by day 12. Cell proliferation studies revealed a dose dependent cytotoxic effect on endothelial cells at 8Gy and 12Gy. In the RGC-5 cell line, cells exposed to 8G showed decreased proliferation at day 5 as compared to control (P<0.05) and subsequently, no significant decrease was observed at day 9 and 12. ROS level was higher in endothelial cells compared with ganglion cells at 8 and 12Gy compared with 2Gy (p<0.05).
Proton beam radiation selectively destroys choroidal endothelial cells while preserving the retinal ganglion cells at 8Gy. This selective destruction of choroidal endothelial cells provide a window of therapeutic opportunity in the treatment of wet form of age related macular degeneration.
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